package lab02.test28;

import java.util.Scanner;

/**
 * Created by ASUS on 2017/11/2.
 */
public class Circle {
    public static void main(String[] args) {
        double a = 0;
        System.out.println("Please input your radius:");
        Scanner scanner = new Scanner(System.in);
        a = scanner.nextDouble();
        System.out.println(a * a * 3.14);
    }
}
